Behavioural and morphological outcome of mild cortical contusion trauma ofthe rat brain: Influence of NMDA-receptor blockade

The authors studied the effect of a mild cortical contusion to the rat brai n on behavioural and morphological outcome and the influence of NMDA-recept or blockade (MK-801, 0.5 mg/kg i.v. 30 min prior to trauma). Spontaneous mo tor activity was assessed 16-18 days post trauma. Saline treated traumatise d rats showed a significant (p < 0.01) hyperactive behaviour compared to an imals without injury. MK-SOI treated rats performed significantly better th an the saline treated animals (p < 0.05). For histopathological evaluation hippocampal hilar neurons were counted, cortical thickness under the impact was measured and microtubule-associated protein 2 (MAP2) immunoreactivity in the dentate hilus was quantified 1, 3 and 21 days post trauma. In trauma tised rats scattered loss of nerve cells, oedema and minute haemorrhages we re present at the site of the impact one and three days after injury. At da y 21 there was a significant reduction of cortical thickness at the site of impact. One day after trauma there was a bilateral, significant loss of ne urons and MAP2. immunostaining in the dentate hilus of the hippocampus. MK- 801 pretreated rats showed similar morphological changes. The disturbed spo ntaneous motor behaviour may be caused by hippocampal damage and a reductio n of somatosensory cortical neurons. NMDA-receptor blockade improved the ou tcome assessed by the functional tests but failed to influence the morpholo gical changes, suggesting that this behavioural test is a more sensitive in dicator of outcome after mild traumatic brain injury (TBI).